The present invention relates to optical data storage disks, commonly used in the data storage and data processing industry. More specifically, the present invention provides an addressing scheme for optical storage disks, which provides for fast addressing and efficient use of disk space.
As suggested above, optical disks are widely used in the data storage industry for various data storage needs due to their versatility and potential high capacities. Examples of such disks include the well-known compact disks (CD), DVD and other optical disks. Within each of these disk types are further variations including writable (or write-once), read only, or rewritable. In each case, the media includes a surface having optical properties that can be easily modified, either by a drive system or during mass production. These modifications are then recognizable when a light source is directed toward the surface of the media.
As with all data storage media, there is a constant pressure and desire to increase data storage capacity. It is well known that the data storage needs are drastically increasing as computer programs and systems become more and more complex. One mechanism for increased data storage is to increase the density of the storage media itself. Naturally, if density increases, capacity on a single piece of storage media will increase without adding additional space. While attempting to increase density on the surface of storage media, it is also necessary to maintain the reliability and repeatability of the storage media. That is, the data should be reliably recorded such that it can be easily and reliably recreated when necessary.
In setting up and managing the space available on the surface of storage media, one consideration is the allocation of addressing space versus data storage space. Addressing and synchronization areas are often required for efficient operation, however they require the use of space on the storage media. Naturally, it is desirable to minimize addressing space wherever possible, thus providing additional space for storing data. Maximizing the space available for data storage increases the density and storage capacity of the media.
One common method of addressing utilized in the optical storage industry is the use of pre-pits positioned at appropriate locations during manufacturing of the disk. These pre-pits are often permanent physical alterations to the media surface, which are detectable. The surface area on the media itself is thus defined such that pre-pits are within a header section and undisturbed areas are provided at other locations for storage of data. Pre-pit addressing does require a certain amount of space on the media surface solely for addressing purposes. As mentioned, it is desirable to minimize the amount of space used for this purpose.
In an effort to increase storage density, and thus capacity, multiple layered storage disks are sometimes used. These disks are constructed to have multiple semi-transparent layers, which can be accessed or identified using appropriate focusing mechanisms and optical components. While multilayer disks are certainly an efficient way to increase density, they create challenges when attempting to devise addressing schemes. This is specifically true when considering the use of pre-pits for addressing, as pre-pit addressing structures can create interference when attempting to access multiple layers on the disk.
As an alternative to pre-pit addressing, wobble structures have been utilized to achieve addressing as well. As is known by those skilled in the art, the surface of an optical storage media will often include a plurality of grooves to allow for easy tracking on the surface of the media. These structures are often referred to as the land and groove portions, which are easily detectable by optical components within the storage drive itself. In certain circumstances, these land and groove portions are “wobbled” or sinusoidal in order to provide additional benefits to the storage media. In one case, these wobbled tracks can then be used for synchronization purposes when writing to and reading from the media itself. Alternatively, these wobble tracks have been used for addressing schemes. In one example, one wall of the groove track is provided with address information. In another example, the wobbles are frequency modulated with address information. The optical systems and readout mechanisms can then detect the placement of these wobbled signals and decode an address there from. These schemes, known as addressing in pre-groove, provide an efficient method of addressing; however, do not necessarily make efficient use of disk space. More specifically, addressing in pre-groove often requires the use of large areas to exclusively provide addressing schemes. In addition, these schemes require complex decoding systems including sampling systems very similar to those used in reading data. The complexity of these systems often create the potential for errors in addressing.
In order to efficiently manage disk space, it is thus desirable to develop a mechanism for addressing that is more efficient and more reliable.